Embodiments of the present invention relate to a semiconductor device, and particularly to a semiconductor device that includes a roll call circuit.
In a semiconductor device such as DRAM (Dynamic Random Access Memory), redundant memory cells are provided in some cases to replace defective memory cells. The addresses of the defective memory cells are stored in fuse circuits. When the addresses are input, the fuse circuits activate a hit signal. After the hit signal becomes activated, the redundant memory cells are accessed instead of the defective memory cells thereby the addresses are relieved.
The addresses to be relieved are programmed into the fuse circuits during manufacturing process. Therefore before shipment, all the defective memory cells are replaced with the redundant memory cells. As a result, all addresses have been assigned to good memory cells. Accordingly, a user does not have to know which address is linked to a defective memory cell.
However, at the time of evaluating or designing the semiconductor devices, someone may need to check, from outside, which address is linked to a defective memory cell, or which defective memory cell is replaced with a redundant memory cell. To meet such a need, a semiconductor device such as DRAM may include a roll call circuit that makes it possible to check, from outside, the addresses programmed into the fuse circuits (see Japanese Patent Application Laid-open No. H05-47196 (Patent Document 1), Japanese Patent Application Laid-open No. 2006-107664 (Patent Document 2), and Japanese Patent Application Laid-open No. 2013-89261 (Patent Document 3)).
However, each of the roll call circuits disclosed in Patent Documents 1 and 2 is configured to output the above hit signal to the outside. Therefore, in order to know which address is programmed into the fuse circuits, all the addresses need to be input to the semiconductor devices. Accordingly, the problem is that it takes time to perform evaluation work by using the roll call circuits. On the other hand, the roll call circuit disclosed in Patent Document 3 succeeds in solving the problem of Patent Documents 1 and 2; the roll call operation is possible without all the addresses being input to the semiconductor device. However, even in the case of the semiconductor device disclosed in Patent Document 3, addresses need to be input to the semiconductor device multiple times during the roll call operation.